Self-driving road vehicles can travel autonomously on a roadway without human intervention, and can at least autonomously maintain lane/road position while avoiding collisions. In some cases, a self-driving road vehicle can also independently navigate along a series of roadways from an initial position to a destination without human intervention; these types of self-driving road vehicles are referred to as “automatic-driving road vehicles”. In other cases, referred to as “assisted-driving road vehicles”, although the self-driving road vehicle can autonomously maintain lane/road position while avoiding collisions, and may also perform some additional driving tasks autonomously, the navigation tasks must be performed by a human operator. Assisted-driving vehicles may be considered to have a more sophisticated form of cruise control. For example, an assisted-driving road vehicle could maintain a constant speed (subject to speed reduction for collision avoidance) within a given highway lane indefinitely, but it would be up to a human operator to take manual control of the vehicle and navigate off the highway at the appropriate exit. The term “self-driving road vehicle”, as used herein, refers to road vehicles that can at least autonomously maintain lane/road position while avoiding collisions, and encompasses both assisted-driving road vehicles and automatic-driving road vehicles.
Self-driving road vehicles rely on an array of sensors and a roadway model representing features of the roadway on which the road vehicle is travelling. The roadway model is derived from survey data of the roadways (e.g., point clouds, geo-referenced images) acquired on an earlier date. The control system, typically incorporating an onboard computer, uses the sensors to obtain data about the environment. Useful information is then extracted from these sensor data by computing hardware and software. The information obtained from the sensors can then be used in conjunction with the roadway model to perform navigation or other autonomous driving functions, including directing the road vehicle along the roadway toward a destination, compliance with traffic signals, speed limits and other legal requirements, and avoiding collisions with pedestrians and other vehicles.
There is a limit to the information that can be extracted from data captured by onboard vehicle sensors. Some relevant information sources may be outside the field of view of those sensors, some information (e.g. legal information) may not be amenable to extraction from sensed data, and there may be practical limits on the amount of sensor data that can be captured and processed in real time. While some of these issues can be obviated with more sophisticated and powerful sensors and additional processing capability, this does not completely resolve the issues and also increases vehicle cost and complexity